Think it's all about the never-ending crisis in Greece and its neighbors? If you're pressed for time, then I'll jump straight to the IMF's key conclusion: "Even absent another European crisis, the most advanced economies still face major brakes on growth. And the risk of another crisis is still very much present and could well affect advanced and emerging economies," notes the IMF in that latest World Economic Outlook.

For U.S. investors, it's crucial to understand that Americans don't live in a vacuum. Problems around the world can wash up on U.S. shores quite suddenly, as every major U.S. company now has extensive global operations. Stumbling economies elsewhere could mean a drop in demand for U.S. exports and even sharp layoffs at the country's biggest employers.

With this in mind, I've compiled a guide to world's economic danger spots. And I'm not talking about the PIIGS (Portugal, Ireland, Italy, Greece and Spain). Those are only the most obvious "at-risk" economies. Several others also hold major risk -- even if they're staying out of the headlines right now.

What's on the mind of the IMF economists? The issues vary from country to country, but include stunningly large budget deficits, deflation, unfavorable demographics, a too-strong currency, and weakening consumer demand.

Before things get better (and they will), they may gate a lot worse over the next few years for some of these countries, so portfolios with exposure to these economies may underperform the broader market.

1. Japan

Roughly two years ago, I laid out the sobering challenges this country faces. A too-strong currency remains as Japan's biggest challenge as years of export-driven growth has led to a currency on steroids. Consider this stat: the Japanese yen has rallied from 120 against the dollar five years ago to a recent 78. This means that anything built in Japan for export, whether it's a Toyota (NYSE: TM) sedan or locally-caught blue-fin tuna is now 35% more expensive to produce.

Now Japan's leaders have to figure out how to boost the country's competitiveness, a task made even more difficult by a recent move to start ending the country's use of nuclear power. Japan instead will have to rely on costly imports of oil and natural gas, sapping cash from other productive uses. Adding insult, Japan is rapidly aging, and as many citizens retire, they are creating a fiscal drag on the government as benefit spending surges.

2. The U.K.

A decision to cut spending in the face of a staggering debt load seemed like a wise move in the U.K., but it was done at a time when the economy was on very tenuous footing. As a result, sharply reduced government spending has caused the U.K. economy to shrink 0.7% in the second quarter of 2012, making the U.S. anemic 1.3% growth rate look downright perky.

The deepening economic slump is leading for calls to relax the current austerity measures, which has the undesirable side-effect of keeping the U.K.'s budget deficits quite large. Unemployment has risen from 5.0% at the start of the global economic crisis to a recent 8.1%, and concerns of a move toward 10% unemployment has renewed memories from the 1970s, when similarly high levels of unemployment led to riots in the street.

And the U.K. can't export its way out of this mess: The country's industrial sector is largely uncompetitive, which explains why the country has run trade deficits every year since 1997. The country is wobbling now, but could easily enter into a downward spiral with a few bad breaks..

3. India

The Indian government has made remarkable strides during the past two decades, boosting literacy rates, expanding access to clean water and other basic health needs, and pushing millions of its citizens above the poverty line. But years of steady economic growth have come at a cost. India is choking on itself as too much economic activity is taking place on a very-stressed infrastructure. Many farm products rot as they remain stuck in warehouses, companies are scrambling to build their own power plants to help keep the lights on, and in some instance, these companies are building their own roads and rail lines to be able to get their goods past key bottlenecks.

But India's greatest problem may be a stubbornly high population growth rate. While family sizes have been quickly falling in countries like Brazil, Indian mothers continue to have many more kids than they can afford to raise, leading to a never-ending wave of job-seeking migrants in to the countries' largest cities. According to the IMF, India's population grew 1.4% in 2011 compared with the previous year. Said another way, India's population stood at 849 million in 1990, and is projected to reach 1.398 billion by 2025. By 2035, India's population is expected to surpass China's, and the country's current infrastructure problems appear likely to worsen.

4. Russia

Russia faces precisely the opposite problem as India: Its population is imploding. In 1990, it had roughly the same number of citizens as Brazil (150 million). But high rates of suicide, death from alcoholism and small family size means that Russia's population is likely to keep falling. By 2025, the Russian population is likely to be just 61% of Brazil's population, according to the United Nations.

Population deflation is just as nefarious as population inflation. Russia will be increasingly hard-pressed to train the next generation of teachers, railway conductors, assembly line workers, farmers, etc. Chinese citizens have already taken note of the emerging Russian vacuum, recently migrating into Siberia to take over fallow farms. The city of Vladivostock in Eastern Russia is now said to have as many Chinese speakers as Russian speakers. This could eventually set the stage for a violent reaction as Russia remains as a highly nationalistic country.

5. Argentina

The Argentinean economy appeared to have a peaked around 1900 when the country was a leading exporter of beef, minerals and many manufactured goods. Decade after decade of bad fiscal policy led to a long slow decline, which only reversed a decade ago when Argentina sharply devalued its currency.

The last decade's gains, may not last though. Argentina suffers from a range of ills, from an inefficient energy sector, crippling tax schemes in key industries, persistently high inflation and a workforce that is increasingly unable to compete with the likes of Brazil, Chile and Colombia.

Many middle-class Argentineans have had enough, packing up for places like Miami, Santiago Chile, London and elsewhere. You won't spot a large population drop as these folks emigrate, as citizens from Paraguay, Bolivia and other neighboring poorer states take their place. Yet Argentina is trading a highly-skilled middle class for a fairly unskilled group of immigrants. And in a global economy, this "brain drain" sets the stage for an even less competitive economy in the years ahead.

6. Egypt and Pakistan

These countries are in the news for geo-political tensions. You don't hear much about their economies, largely because each is the beneficiary of massive amounts of foreign aid that helps keep them out of the economic crisis zone. Yet chances are rising that this aid will be sharply reduced or even eliminated as their respective governments increasingly choose to pursue independent geopolitical strategies that diverge from the stated goals and wishes of key aid providers.

The negative effects on Egypt could be especially severe. Under former President Hosni Mubarak, Egypt had reasonably competitive banking and telecom sectors and a very strong tourism sector. Nowadays, with many of the country's leading executives residing elsewhere (due to their former close affiliations with President Mubarak), the business class in Egypt is under pressure. And tourism, a key source of foreign earnings, has virtually dried up while global travelers steer clear of the current socio-political tensions. Egypt increasingly looks in need of even more foreign aid than it currently gets, though that option may not be available to the government.

Action to Take --> Unless these countries address long-term endemic problems, their futures look set to darken further.

You should keep an eye on each of these countries, because as I said earlier, their problems could affect the global economy -- and in turn your own portfolio.